This photo shows Engine 3F without insulation. I normally operate this engine inverted so the hot end of the displacer (the top of the black cylinder) is normally at the bottom, just above a heat source.
You can find lots more photos and information on Engine 3F in articles on this website. I don’t offer any plans for this engine. It’s an evolution of the original Engine 3. It will put out a reliable one watt of power all day long.